Two-step electro-thermochemical cycle for CO2 splitting in a solid oxide electrochemical cell

Solar CO2 splitting via a two-step thermochemical cycle (TSTC) has emerged as a promising technology for solar fuel production. However, the extreme reduction temperature (Tred) required to achieve optimal CO yields poses challenges in reactor design, operation, and solar-to-fuel energy efficiency. In this study, a two-step electro-thermochemical cycle (TSEC) for CO2 splitting into CO using a solid oxide electrochemical cell (SOEC) is presented with the objective of reducing Tred and improving solar-to-fuel energy efficiency. The investigations reveal that TSEC exhibits the capability to decrease Tred from 1500 °C to 1000 °C, while simultaneously maintaining a substantial CO yield of 550 μmol/g. Moreover, the efficiency analysis demonstrates that TSEC achieves a superior solar-to-fuel energy efficiency of 20.4 %, outperforming 4.1 % of conventional TSTC. In sum, this study demonstrates a novel approach to solar fuel production, enabling high and stable CO2-to-CO conversion at moderate temperatures while maintaining high energy efficiency.